The present invention relates to the sealing of pipe repair clamps.
More particularly, the invention provides a flexible inner sheet or sleeve adapted for duty inside a pipe repair clamp to prevent leakage of the fluid to be transported in a pipeline. The inner sheet or sleeve of the present invention may be used in combination with a band-type pipe clamp of the type described in one of our co-pending applications, but is not limited thereto.
The clamp is also useful for temporary or permanent repair of a leaking pipe, and for connecting two pipe ends.
Pipe clamps are usually, although not always, expected to provide a liquid-proof seals in addition to their primary function of mechanically repairing a pipe or holding a pair of pipe ends together co-axially. Sealing is often provided by use of a rubber sleeve along the whole length of a tension-band type clamp or coupling. A known difficulty with seals of this type is that due to extreme pressure the rubber tends to extrude axially out of the clamp. Furthermore, the simple sheet or sleeve type of seal does not operate well, or cannot be assembled over a pipe diameter different from the nominal design diameter.
The state of the art can be assessed by review of a selection of recent US patents.
In U.S. Pat. No. 4,717,182 Behrens et al. address the joining of asbestos-cement pipes by use of a plastic coupling sleeve reinforced with glass fibers. The pipes to be joined have external grooves which are utilized by a cable-like connecting member.
A coupling intended for collection pipes used for gravitational sanitary drainage is disclosed by Barbe et al. in U.S. Pat. No. 5,248,169. A flexible elastic and reversible collar is retained inside a rigid binding ring. The arrangement is not intended or suitable for the high forces encountered by large pipe couplings.
The pipe coupling sleeve disclosed by Hendrickson in U.S. Pat. No. 5,282,654 refers to a pair of pipes, at least one of them being plastic. The design is directed at preventing damage to the plastic pipe and requires that the pipe ends have circumferential grooves.
Webb et al. disclose a coupling having a sealing sleeve in U.S. Pat. No. 5,772,257. The sealing sleeve has two sets of inwardly projecting ribs to effect sealing against the pipes. The coupling requires radial abutment surfaces for operation.
A pipe coupling able to connect pipes having unprofiled end sections is disclosed by Schmidt in U.S. Pat. No. 6,070,914. Sealing is effected by a pair of gaskets. However the clip strap has inwardly directed flanges which limits the flexibility of the device. The coupling has many components.